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AD1580BRTZ-R2 データシート(PDF) 9 Page - Analog Devices |
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AD1580BRTZ-R2 データシート(HTML) 9 Page - Analog Devices |
9 / 12 page AD1580 Rev. F | Page 9 of 12 TRANSIENT RESPONSE Many ADC and DAC converters present transient current loads to the reference. Poor reference response can degrade the converter’s performance. Figure 22 displays both the coarse and fine settling characteristics of the device to load transients of ±50 μA. (a) (b) 1µs/DIV 1mV/DIV 20mV/DIV IR = 100µA – 50µA STEP IR = 100µA + 50µA STEP 1mV/DIV 20mV/DIV Figure 22. Transient Settling Figure 22a shows the settling characteristics of the device for an increased reverse current of 50 μA. Figure 22b shows the response when the reverse current is decreased by 50 µA. The transients settle to 1 mV in about 3 µs. Attempts to drive a large capacitive load (in excess of 1000 pF) may result in ringing, as shown in the step response (see Figure 23). This is due to the additional poles formed by the load capacit- ance and the output impedance of the reference. A recommended method of driving capacitive loads of this magnitude is shown in Figure 20. A resistor isolates the capacitive load from the output stage, while the capacitor provides a single-pole low-pass filter and lowers the output noise. 1.8V 2.0V VIN CL = 0.01µF 50µs/DIV 10mV/DIV Figure 23. Transient Response with Capacitive Load PRECISION MICROPOWER LOW DROPOUT REFERENCE The circuit in Figure 24 provides an ideal solution for making a stable voltage reference with low standby power consumption, low input/output dropout capability, and minimum noise output. The amplifier both buffers and optionally scales up the AD1580 output voltage, VR. Output voltages as high as 2.1 V can supply 1 mA of load current. A one-pole filter connected between the AD1580 and the OP193 input can be used to achieve low output noise. The nominal quiescent power consumption is 200 µW. 3V 34.8k Ω AD1580 OP193 VOUT = +1.225V OR VOUT = +1.225 (1 + R2/R3) R3 R2 4.7µF 205 Ω Figure 24. Micropower Buffered Reference USING THE AD1580 WITH 3 V DATA CONVERTERS The AD1580 low output drift (50 ppm/°C) and compact submi- niature SOT-23 package make it ideally suited for today’s high performance converters in space critical applications. One family of ADCs for which the AD1580 is well suited is the AD7714-3 and AD7715-3. The AD7714/AD7715 are charge- balancing ( ∑-∆) ADCs with on-chip digital filtering intended for the measurement of wide dynamic range, low frequency signals such as those representing chemical, physical, or biological processes. Figure 25 shows the AD1580 connected to the AD7714-3/AD7715-3 for 3 V operation. AD7714-3 AND AD7715–3 AD1580 3V 34.8k Ω REFIN(+) REFIN(–) HIGH IMPEDANCE >1G Ω RSW 5k Ω (TYP) CREF (3pF TO 8pF) SWITCHING FREQUENCY DEPENDS ON fCLKIN Figure 25. Reference Circuit for the AD7714-3 and AD7715-3 |
同様の部品番号 - AD1580BRTZ-R2 |
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同様の説明 - AD1580BRTZ-R2 |
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